Blood filtration unit

ABSTRACT

A blood filtration unit for filtering multiple units of blood comprising means for attaching the unit to a blood reservoir, a drip chamber and a segmental filtration compartment for filtering blood.

BACKGROUND OF THE INVENTION

In the administration of whole blood to a patient it is desirable, ifnot necessary, to filter the blood as it is being administered. Thedebris which is to be removed by the filter will vary depending upon thelength of time the blood has been stored. Over the years, many differentfilter media have been developed which are specifically useful infiltering debris from whole blood. Although the engineering of thefilter media and the filter efficiency is extremely important there area number of other problems involved with the filtering blood duringblood transfusions. First, in administering blood to the patient and infiltering this blood, the flow rate should be known and controlled. Thefiltration unit should be readily insertable into a blood reservoir,usually a blood bag, and the necessary administration sets foradministering blood to the patient easily and readily connected to thefiltration unit in a manner that does not disrupt or change the flow ofthe blood. The filtration unit should be constructed so not to collector entrap micro-gas bubbles which might be administered inadvertently tothe patient. The unit itself should have a low total volume so the bloodis not held in the unit and all of the blood from a blood bag isadministered to the patient. The filtration unit should be easily andreadily primed and primed in such a manner as not to entrap gas bubbles.Along with all of these problems which should be overcome, the unitshould have excellent filtering efficiency, do as little damage to theblood components as possible, and be usable for multiple bloodtransfusions to a single patient in order to be reasonably economical.

SUMMARY OF THE PRESENT INVENTION

We have discovered a new and improved blood filtration unit. The flow ofblood through our unit is measurable and known. The efficient manner inwhich the filter media is used in our unit is improved, and the possibleblockage of the media is reduced. Our new filter unit does little, ifany, damage to the blood components being filtered. In certaiinembodiments of our new filter unit, it may be readily and easily primedor filled without entrapping gas bubbles and filtered blood may bedrained from the unit so there is very little blood held-up or retainedin the unit and substantially all the blood is available in the patient.In other embodiments of our new filtration unit administration sets areeasily insertable into the filtered blood outlet in a manner thatinsures a uniform flow rate and reduces the possibility of entrapment ofmicro-gas bubbles by the filtered blood stream. Our blood filtrationunit may be used for multiple administration of units of blood and iseconomical.

In accordance with the present invention, our new blood filtration unitcomprises a filter cartridge disposed within a filter housing. Attachedto the top of the filter housing is a drip chamber for measuring bloodflow. Attached to the top of the drip chamber is the blood inlet whichextends into the chamber at its one end and is diagonally cut at itsopposite end for easy insertion into a blood reservoir such as a bag ofblood. The filter cartridge comprises filter media, a top end cap forsealing one end of the media and a bottom end member to seal theopposite end of the media but leave a hollow center core of the mediaopen and directly connectable to the blood outlet. The bottom end memberattaches to the housing to form the completed filtration assembly. Thetop cap is multipointed or star-shaped and has a diameter measured atthe end of the points substantially the same or slightly smaller thanthe inside diameter of the housing. The filter cartridge is elongatedand has a hollow center core. It's cross-sectional shape issubstantially the same as the multipointed shape of the top end cap. Thebottom member seals the bottom of the filter media and closes thehousing. There is a centrally located outlet in the bottom member whichconnects directly to the center core of the media and to which anadministration set may be connected. In use, blood flows from the bloodbag to the drip chamber, down through the openings created by themultipointed filter cartridge into the segmented filtrationcompartments, through the media into the hollow center core and outthrough the blood outlet in the bottom end cap. In certain embodimentsof our new blood filtration unit, a filtered air vent valve is placed inthe side wall of the drip chamber so the unit may be readily primed andfilled and entrapped gas evacuated. When the blood bag is emptied, thevalve may be opened and the filtration unit drained to allowadministration of substantially all of the filtered blood. When the ventvalve is opened, the incoming air is filtered.

In certain embodiments of the blood filtration unit of the presentinvention, the blood outlet has a shoulder on its inlet side. The insidediameter of the outlet measured at this shoulder is the same as theinside diameter of the tubing of the administration set to be used withthe unit to administer blood to a patient. This construction reduces thepossibility of micro-gas emboli being entrapped in the area where theblood outlet and the administration set meet. This construction alsoprovides for a uniform and constant flow rate of blood to the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in conjunction with theaccompanying drawings wherein:

FIG. 1 is an exploded view in perspective showing the assembly of thevarious parts of the new blood filtration unit of the present invention,

FIG. 2 is a cross-sectional view of a blood filtration unit according tothe present invention,

FIG. 3 is an enlarged, cross-sectional view of a filter air vent valvein accordance with the present invention with the valve in the closedposition,

FIG. 4 is an enlarged, cross sectional view of the air vent valve shownin FIG. 3 with the valve in the open position, and

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 3.

The same numeral has been used for similar parts throughout the Figures.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings in FIG. 1, there is shown a blood filtrationunit in accordance with the present invention. At the top of the unit isthe blood inlet 11. One end 12 of the blood inlet is tapered ordiagonally cut for easy insertion into a reservoir of blood such as theplastic blood bags commonly in use. The blood bag contains a weakenedportion, circular in shape, and the tapered spike-like inlet is readilyinsertable into this weakened portion. The opposite end of the bloodinlet extends into the drip chamber 13 which is at the top of thehousing 14 for the unit. As may be more clearly seen in FIG. 2, theextension 15 into the drip chamber 13 allows blood to drip into the unitand the number of drops may be counted and metered as desired. Theheight of the drip chamber should be as small as possible to reduce theimpact force of the blood droplets on the distribution surface andminimize the blood-air interface contact time in order to reduce bloodtrauma.

Disposed in the side wall of the drip chamber is an air vent valve 17..The valve is more clearly shown in FIGS. 3, 4, and 5. The valvecomprises a resilient member 18 which extends through a hole 19 in thewall 20 of the drip chamber and expands outwardly to seal along theinside surface of the wall. On the outside surface of the wall andaround the entry hole is a circular ledge 21. An annular shaped filtermedia 22 is positioned within the circular ledge. The media contacts thewall surface on one side and the resilient member on the other side. Thecircular ledge carries an opening 23 to allow air to escape or enterthrough the valve. When the filtration unit is to be filled, theresilient member is pushed in as shown in FIG. 4, allowing air withinthe unit to escape out through the entry hole and the opening in thecircular ledge. A number of stops 24 are disposed about the entry holeto prevent sealing of the hole when pushing in the resilient member.When the unit is filled to a desired level with blood, the valve isreleased and automatically closes. To drain the unit, the valve ispressed inwardly to allow air to enter the blood filtration unit andallow the unit to drain. The air entering the unit is filtered throughthe annular filter media.

Disposed from the drip chamber is the portion of the housing thatencloses the filter cartridge. The filter cartridge itself comprisesfilter media 25, a top end cap 26 and a bottom member 27. The top endcap is solid and multipointed or star-shaped. It is preferred that theend cap have from about four to ten points to produce between four andten segmental filter compartment areas in the unit. The media is in theform of an elongated member having a hollow center core. Itscross-sectional shape is the same as the multipoint shape of the top endcap. If desired, a permeable center core 28 may be disposed in the mediafor structural purposes and such a core may be wrapped with a fine mediato aid in the filtration as desired. One end of the media is sealed bythe top end cap and the other end of the media is sealed into the bottommember. The outer periphery 29 of the bottom member 27 is attachable tothe housing 14. The bottom member contains a centrally located outlet 30which connects to the center core of the media at one end with the otherend 31 adaptable to connect with various types of administration sets oradministration set tubing.

In one embodiment of the present invention, the outlet is constructed asshown in FIG. 2. Within the blood outlet 30 there is a small shoulder 33which extends into the opening. The inside diameter of this shoulder isexactly the same as the inside diameter of the tubing 34 of theadministration set to be used. The tubing is inserted in the downstreamside of the outlet up against the shoulder. If desired, the tubing maybe adhered or bonded to the inside surface of the outlet. Also, ifdesired, the outlet may be slightly tapered to aid in insertion. Anadvantage of this construction is that no air can be entrapped where thetubing and the blood outlet meet and this eliminates the possibility ofentrapping small air bubbles during administration of the blood. Thisconfiguration also provides a uniform diameter from the filtration unitto the needle administering blood to the patient and a constant anduniform blood flow.

The housing for the filter unit may be made from any of the plasticmaterials which are inert and have no effect on blood. Examples of suchmaterials are the polycarbonates, the butadiene-styrenes and the like.Similar materials may be used for the top end cap and the bottom endmember. Generally, it is preferred to use clear materials for thehousing.

The filter media which may be used with the unit are any of the variousdepth, semi-depth, or sieve type medias or various combinations of thesemedias. Suitable media are woven fabrics made from synthetic filaments,foam materials, nonwoven fabrics and the like. A preferred filter mediafor the transfusion of blood is a combination of a woven polyesterfabric having a mean pore size opening of 160 to 180 microns as thefirst or upstream layer. The second or downstream layer is aneedlepunched nonwoven fabric of polyester fibers weighing about nineounces per square yard. The layers may be separated by an open plasticmesh material for support and stability. In some instances, a third orfurther downstream layer may be used such as a woven nylon fabric havinga mean pore size rating of about 20 microns. This media is used toprevent lint or fibers which may sluff off or be removed from thenonwoven media from entering the bloodstream. If desired this media maybe wrapped around a supporting core to act in the way described.

The air vent valve is made from resilient material which is inert toblood such as natural, synthetic or silicone rubber. The valve isresilient and readily deformable and provides a good seal with thematerial from which the housing is made. The air filter media used withthe valve may be any of the standard air filtration materials such as aneedlepunched polyester or other synthetic fiber batts and the like.

In our new filtration unit, the design is important in order to reducethe holding capacity of the unit itself while providing good flowcharacteristics for the filtration of blood. The drip chamber is assmall a diameter as possible and is flared out to the filter cartridgeto provide good flow characteristics. During use, it is preferred thatthe blood level be maintained above the top cap of the filter cartridgeso that blood drops hit a liquid surface rather than a solid surface toreduce the possibility of blood damage. The filter cartridge isstar-shaped to provide a large filtration area and good filtrationefficiency while also maintaining the volume as low as possible. Aspreviously mentioned, from about four to ten points may be used toprovide the necessary area of filtration. The points of the star aresubstantially in contact with the inside suface of the housing. Thisconfiguration produces the same number of filtration compartments asthere are points on the end cap. The blood from the filter bag can flowinto all of the filtration compartments. Should the filter media in oneof these compartments start to become blocked, the remainingcompartments are still available for filtration and provide forefficient filtration, even as the media may become blocked.

Having now described our new blood filtration unit, it will becomeapparent to those skilled in the art of the many variations and changesthat may be made without departing from the spirit and scope of thepresent invention. All we desire to be limited to is that described inthe appended claims.

What is claimed is:
 1. A blood filtration unit comprising a housing fora filter cartridge, a blood inlet disposed from said housing, one end ofsaid inlet extending away from said housing and attachable to areservoir for blood, a filter cartridge disposed in said housing, saidcartridge comprising a top end cap, a bottom member, and an elongatedfilter media having a hollow center core sealed between said top cap andbottom member said filter media being selected from the group consistingof woven fabrics, nonwoven fabrics, foam materials, and combinationthereof, said top end cap being solid and having a multipointedconfiguration, said filter media having substantially the samecross-sectional shape as the top end cap, the outside diameter of thetop end cap as measured at the points being substantially the same asthe inside diameter of the housing, said bottom member having acentrally located blood outlet, one end of said outlet connecting withthe hollow core of the filter media, the other end of said outlet beingadaptable to a blood administration set, and said housing being securedto said bottom member at the periphery of said bottom member.
 2. A bloodfiltration unit according to claim 1 wherein the end of the blood inletfor attachment to the blood reservoir is tapered for easy insertion intothe reservoir.
 3. A blood filtration unit according to claim 1 whereinthe filter housing is cylindrical in shape.
 4. A blood filtration unitaccording to claim 1 wherein the filter cartridge has from four to tenpoints.
 5. A blood filtration unit according to claim 1 wherein thefilter media comprises a multi-layer media with the upstream mediacomprising a woven nylon fabric having a pore size rating of 170 micronsand a downstream media of a needle-punched synthetic fiber fabric.
 6. Ablood filtration unit according to claim 5 which includes a furtherdownstream filter media of a woven synthetic filament fabric having apore size rating of 20 microns.
 7. A blood filtration unit according toclaim 1 wherein there is a drip chamber disposed at the upper portion ofthe housing and the opposite end of the blood inlet extends into thedrip chamber.
 8. A blood filtration unit according to claim 7 whereinthere is a filtered air vent valve disposed in the side wall of the dripchamber.